This interactive key provides diagnostics for all the species of spider mites (Acari: Tetranychidae) previously recorded in Australia, based mostly on literature records. Several species collected in Australia, but not yet recorded in the literature, are also included (manuscript in prep). In addition, a few select exotic species from south east Asia of concern to Australia’s biosecurity have also been included. Where possible, the diagnostics (images and data) presented in this key were taken from direct examination of the type specimens. A detailed fact sheet has been provided for nearly all species treated. Australian voucher specimens have not been examined for all species treated in this key, and some records are in need of further investigation.